WILD LETTUCE 43 



one is the subject of this article, the prickly 

 lettuce, a native of the old world, the other is 

 the rosin weed, which is indigenous to the 

 new world. The latter (Silphium lacinatum 

 L.) occurs on the western prairies from Ohio Another com- 

 to the Rocky mountains. It is a large, coarse P^^ P^^* 

 plant, but yet an attractive one, with sun- 

 flower-like heads. It is usualh^ known as 

 rosin weed, from the resinous exudation, 

 which children gather and convert into a 

 white palatable chewing-gum. 



So strong isthepolarity of the leaves of this 

 plant that it has repeatedly served a very 

 useful purpose in providing travelers with 

 their bearings when lost on the prairies during 

 dark nights or cloudy days. This character- 

 istic was familiar to pioneers long before Gen. 

 Alvord of the U. S. Army made it known to 

 the scientific world in 1842. Longfellow, 

 upon hearing of the plant and its service to 

 travelers, made it the basis of some lines in 

 Evangeline : 



"Look at this vigorous plant that lifts its head from 

 the meadow, 



See how its leaves are turned to the north, as true as 

 the magnet ; 



This is the compass flower, that the finger of God has 

 planted 



Here in the houseless wild, to direct the traveler's jour- 

 ney 



Over the sea-like, pathless, limitless waste of the des- 

 ert." 



Unfortunately the poet at first misappre- 

 hended the real character of the plant, with 



